The present invention relates to basic composite unburned bricks produced by integrally molding magnesia-carbonaceous refractory and basic refractory.
In modern electric arc furnaces, fire bricks, particularly the ones at hot spots, are susceptible to damage by heat or melting due to intense heat associated with the high-voltage operation now established wth the development of operation technique. As a countermeasure to this problem magnesia-carbonaceous bricks had been used with successful results. However, the process for operating electric arc furnaces has recently developed further into the ultra-high-voltage operation. This has required the use of expensive high-purity magnesia-carbonaceous bricks at hot spots or slag line instead of the conventional magnesia-carbonaceous bricks. Generally, areas where bricks have got damaged by heat are dismantled and re-built with new bricks. This means a considerable waste of expensive high-purity magnesia-carbonaceous bricks.
One method to cope with this problem is to use shorter bricks than the conventional ones. In this case, however, it is necessary to arrange the shorter bricks so as to project inwardly of the furnace and to fill the space between the furnace shell and the bricks with powdery magnesia. This requires very complicated process and much skill. Another method is to arrange such short bricks without any spacing from the furnace shell. However, this leaves the bottom of the water-cooling jacket exposed, resulting in water leakage therefrom.
The Japanese utility model publication SHO 44-28136 discloses basic bricks having a hollow formed therein by molding a brick with a filler metal embedded therein and removing it after molding. However, this molding process was troublesome and time-consuming. The publication also describes that for use at areas exposed to severe damage, such a hollow may be filled with magnesia clinker. In this case, however, the clinker is merely filled, not compacted by pressure molding. Such bricks would be of no practical use under the modern stringent working conditions.